I have had a normal suspension 300E , 1990. I replaced Comforts with HD's . Ride quality was firmer and not harsh by any means. Typical stock large gap between top of tire and bottom of fender. Does Sportline lower the car?
Absolutely. Don't know how much, but the Sportline looks much better to my eye. Wheel gaps much less.

I have had my '92 Sportline for about 4 years now. The springs are shorter and stiffer than stock. Control arm bushings are stiffer, sway bars larger diameter. Ride quality?

The standard MB Sportline shocks provide an excellent compromise between handling and harshness. I replaced them with Bilstein Sports about a year ago. The handling is stiffer. There is more harshness. V-Rated tires now somewhat irritating on certain interstate roads. Handling, however, is superb.

I also have a '93 Sportline that is still all stock. I don't drive it much at all, but it's ride quality is better than the '92 with the Sport Shocks.

So I would think that mixing components without knowing what will work with what could be an expensive exercise. For instance, the valving in Sports Shock is engineered to work with shorter, stiffer springs. Shocks need to match springs. If you do the springs and not the sway bars, then you have left out a piece of the puzzle.

Steve